Changing index of a cell - ios

Question

I'm starting to work with UITableViews and can't seem to find out how to change the position of a cell with code. Changing the position in the storyboard is straightforward enough but I need to be able to do it in swift.

Answer 1

TLDR;
Update your data. i.e. swap(&arr[2], &arr[3]).
Call the tableView's reloadData() method to reflect the changes to your data.
Long answer
An instance of UITableView works by checking its data source (UITableViewDataSource) for the information it needs. This includes the number of sections and rows, as well as the instance of UITableViewCell that the table view is to use. These are defined by the following UITableViewDataSource delegate methods:
override func numberOfSectionsInTableView(tableView: UITableView) -> Int;
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int;
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell;
Usually, you would base the former two on some data you have, likely an Array or similar container. For example, if your tableView displayed data from an Array named fruitArray (which contained names of different fruit - a list of strings), then you might have something like the following:
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// Our array is one dimensional, so only need one section.
// If you have an array of arrays for example, you could set this using the number of elements of your child arrays
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// Number of fruits in our array
return fruitArray.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("yourCellId") // Set this in Interface Builder
cell.textLabel?.text = fruitArray[indexPath.row]
return cell
}
Then, you can see that the answer to your question becomes simple! Since the contents of a given cell are based upon fruitArray, all you need to do is update your array. But how do you get the tableView to "recheck" its dataSource? Well, you use the reloadData method, like so:
swap(&fruitArray[2], &fruitArray[3])
tableView.reloadData()
This then triggers the tableView to "recheck" its dataSource, hence causing your data swap to appear on the screen!
If you'd like the user to be able to swap the positions of the cells, you can use the following UITableViewDelegate (not UITableViewDataSource) delegate method:
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool
Have a look at this article for more info. You can also view Apple's documentation on UITableView, UITableViewDataSource, and UITableViewDelegate for further detail.
Hope this helps!